Nozzles for the production of fine parallel jets



Feb. 16, 1960 J. M. CUNNINGHAM 2,925,224

NOZZLES FOR THE PRODUCTION OF FINE PARALLEL JETS Original Filed March 28, 1957 2 Sheets- Sheet l 1N VEN TOR.

JGSEP/l Al. CU/V/V/IVGl/JM BY United States Patent NozzLEs FOR THE PRODUCTION OF FINE PARALLEL JETS Joseph M. Cunningham, Wilkinsburg, Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware Continuation of application Serial No. 649,188, Mar h 28, 1957. This application November 19, 1958, Serial No. 774,877

9 Claims. (Cl. 239-548) orifices directing a high velocity flow of liquid from the nozzle with high directive accuracy, i.e. accurately square with the nozzle dimensions and without deflection or deviation in direction, and which, where a multiple arrangement of orifices is employed produces small accurately-parallel high-velocity jets that may be made to impinge with precision on a target or into a small space.

This application is a continuation of application Serial No. 649,188, filed March 28, 1957, now abandoned, said application being by the same inventor and the same assignee as the present invention. It is common experience that a high-velocity jet or liquid stream emerging from a small hole under high pressure ofttimes goes ofi in a peculiar askew direction, and in fact the direction may change with pressure, the jet may break up into a succession of high speed droplets,

or be otherwise unstable and unpredictable particularly with respect to direction and continuity of the jet. While it is apparent that these variations are due to the nature of the hole or nozzle from which the jet emerges, no way has heretofore been known to avoid these accidental variations. It is the primary purpose of this invention to provide orifice profiles whose use insures a high degree of precision in the direction of the emerging jet and a high degree of cohesion in the jet so as to reduce the tendency to break up into droplets. Y

By way of example, one application in which directive precision and cohesion of a high-velocity jet is. important is in directing cutting fluid into the narrow angular clearance space between a metal-cutting tool and a work piece to strike with high impact efiect at the line of cut. By employing nozzles of this invention an accuratelydirected high-velocity jet maybe placed with precision in the extremely small space at the apex of the cutting.

tool clearance angle, and by employing a linear array of such nozzles a plurality of small accurately-parallel high-velocity jets maybe placed in the clearance space along the'line of cut and substantially at right angles thereto.

In the above-mentioned example of applying highvelocity jets of cutting fluid to a cutting tool, it is 2,925,224 Patented Feb. 18,1960

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2 inasmuch as any side splash will greatly reduce the impact energy of the jet. The kinetic energy. of the needle-like jet, upon impact and abrupt turning of the stream parallel to the cutting edge, is converted into useful static pressure which assists in forcing the fluid over the cutting edge of the tool, notwithstandingthat the pressure of the tool entering the work may be fifty thousand pounds per square inch or higher. The patent to R. J. S. Pigott, No. 2,653,517, discloses such a system and-discloses the use of a sharp-edged orifice or short rounded-approach orifice to form a thin, non-spreading jet for this purpose. Moreover, the emerging jet must be of such form that its venacontracta is far enough from the nozzle so that the latter may be placed in the limited space available between the tool-carrier and work piece being cut.

The manufacturer and mounting of nozzles provided with such orifices present serious problems. The orifices are extremely small, being less than A in diameteran'd usually of the order of .018 to .033 inch in diameter. Even slight imperfections due. to roughness, which destroys the symmetry of the, orifice, or due to inaccurate direction of the drilled hole, are highly magnified in the efflux and result in mid-directedjets, whereas, if nozzles are to, be readily replaceable without special fitting and adjustment, they should project jets which are square a line at the apex of the clearance angle in order that the static pressure developed by impact may be applied over the entire width of the cutting edge of the tool. Multiple jet nozzles having sharp-edgedorifices and also those having straight-drilled, short-tube orifices, when subjected to pressure-pattern tests, revealed a high frequency of nonparallel jets probably caused by unavoidable variations in the minute dimensions involved. Attempts which were made to re-direct or straighten the jet streams by reaming were not successful and, furthermore, the jet dimensions were destroyed requiring complete remaking of the nozzles. By way of illustration 1000 man-hours were required to produce a nozzle having two parallel jets when sharp-edged orifices were used, whereas only 10 man-hours were required to produce a nozzle having two parallel jets using orifices shaped according to this invention.) i

An object of the present invention is to provide a nozzle with an orifice capable of discharging a highvelocity needle-like jet whose direction is square with the nozzle dimensions, so, that the nozzle may be readily aimed to direct the jet to a desired location, whereby replacementor substitution of the nozzle may be made without laborious trial and adjustment of its mounting such as would be required to compensate for orifice variations which are commonly encountered where dimensions are small. v

Another object of this invention is to nrovide an orifice profile such that a nozzle with multiple orifices will produce accurately-parallel jets giving substantially the same pattern at impact as at emergence.

A further object of this invention is to provide an orifice which produces a high-energy jet by flow of fluid under pressure through a passage of small convergence such that the boundary flow does not separate from the .bf ig high" pressure" at? j' subs'tantially comp wallof thepassage and thelines of .flowarecansed to. continue to converge after the jetted fluid leaves the noz zle, resulting in increased velocity of the jet at a distance remotefrom the emergence opening as compared with a nozzle which develops maximum velocity approximately at emergence of the jet.

A still further object of this invention is to provide a nozzle capable of dischargirig a high-velocity needle-like :iet which; hasa. high xieg eto wh re e d hiqh ma projected considerable distance without breaking up :i 1tQd P1 I. ,Qth er objects and advantages QiihgfinVQi'ltiQn will appear f ro1r ,the, following description and accompanying rawinssl w i h; 1' r Figure l is aside viewpartly in section of one form nozzle having a single orifice of circular transverse ,tfi urefiris n ndrv e l iw r 9 nozzle having s a l q fi wffii u r PSYQI Q F iQE -Fig ure is a longitudinal sectional view taken along ne III-III of Figure'2 and showing the-general form of theorifice I I p ure- 4 is anjend view of a second form of nozzle embodying the present invention, having multiple circular orifices .for producing parallel jet streams;

Figure .5 is a seetisim view -taken along line V-V Figure 6 is a sectional tie'wertmjoi m plate formed 'gvvith, a series vof circular orifices each provided with an f F'g'urej is a cross sectionof anforific'e which'hasa }linear taper profileaccording to one embodiment of this invention; I f I I I I ,Fignre 8"is' a cross section of anorifice which has a ,curved-taper profile according'to another embodiment "of this invention;

Figure 9. is a. cross. section of an orifice whose profile a'corribination'of linear taper with elliptical entrance accordin toan'other embodimentof thisfinvention; and ,Figu're' 1 0 is a cross sectioniof 'an orifice whose profile ,is'.a combination, of curved taper with eIIiptiCalentrance "according to another embodiment of this invention.

Referring more particularlytov the drawings, .Figure hows a des irablefandconvenient form, of nozzle as- 'sem bly.r The nozzleproper comprisesfa flat orifice plate "or disc l0, a portion 11 ofwhich 'may be of reduced eterto provide an annular shoulder'12 seated on nipple .13 and soldered or. brazed thereto as at '14. ,'The Zopposite. end of the nipple I13 'fits within a pipeflS to "the limited extent permitted by an annularflange 16 which ts the threaded end offthe'pipe. The nipple "13, is :secured to the pipe 15 by a nut 17 and may'beprovided ith a' e fzfl ri v n leakage,-

. I s .Qr fis 9 E1 0 o hey T 9 shown f u e 1 and in enlargeddetail in Figures 2 3, is of the. order of 7 to inch'thick and is formed with an orifice 18 which circular incross-section and which tapers "from approximately,Q.O24. inch diameter at, entrance to fapproximateiy inch at emergence. These measure- Tqnents are giv en here as, merely exemplary to indicate the order of size, the orifices of this invention being'smaller elliptical entranceprofiie;

2/1 inch diameter and havingv a. profile "shape to be described in detail later... These dimensions indicatejthe al s c ths rifice ew t .t 't P r o s fithis invention, which remove it entirely from the category of nozzles of general utility. It'willbe readily appreciated that accidental variations in the va'r'iousfdimensions' of such a' srriallorifice mayproduce a relatively large or eifect on. a V jet 'feme rging" therefrom; under gh velocityf Ithas been-round that ties the characteristic ofjiflow'is in such small v '4 .This. invention is characterizedby having-a nozzle orifice less than 4 inch diameter whose profile shape is such that small variations therein produce a minimum street on the emerging jet, particularly as to direction of the jet, as well as to its stability and convergence contour. The invention is further characterized in producing jets whose vena contractais far from the orifice plate which insures that the jet will have a high ratio of delivered energy to input energy. Furthermore, the orifices converge gradually from entrance to emergence and are sufficiently short to have low loss whereby high delivered energy is attained in the jet.

In Figures 4 and 5 the orifice plate 19 is formed with two circular orifices 20 and 21, each o f which tap er s .frornthe inlet side to produce gradual constriction of'the respective flow streams andtheir projection in accuratelyparallel jets. It is apparent that the nozzle 13 (Figure 1 may be properly'proportioned to have an'orifice plate at larger dimensions which is provided with a'n'yfldesired larger number of orifices such as 18, 20 and 21. The orifices may be located on any desired pattern and for the above-mentioned purpose of directing cutting oil into the clearanceof a cutting tool a linear arrayis desirable, ,for example as illustrated in Figure 6 by the array of orifices 22.v When the orifices are formed as herein specifiedandare manufactured with ordinary closemech- .anical tolerances, the resulting jets will be accurately .ment of cutting oil in that the vena contracta of the emerging jet is a considerable distance fromithe emergence opening of the orifice plate. This means thatthe sides of the jet continue to contract even after leaving the orifice with resultant increase in kinetic energy of the s tream. Under high motivating pressure the vena contracta may be several inches from the orifice plate, wiih the result thatthe nozzle 13 (Figure 1), though placed some distance from the target, e.g. cutting tool, still'is able to develop a jet whose maximum velocity or kinetic 'energy is concentrated exactly at the target, i.g. point of impactunder the cutting edge of the tool. It has been found that the minimum distance of the vena contracta for the orifices of this invention is from 10 to 50 times larger than the corresponding distance from a thin-disc orifice, and at high operating pressures at which the orifices of this invention are normally used the 'vena contracta has been found to be located from 1 /2 to 3 inches downstream from the outlet opening of the orifice plate .10 (Figure 1), thus permitting placing the nozzle so as to take advantage of the "maximum kinetic energy of'the jet. In other words the orifices herein disclosed provide a high. ratio of kinetic energy in the jet to orifice input energywherebythe vena contracta is displaced downstream a large distancesutficient to permit location of the nozzle at the most favorable location, which could i this invention relates, the boundary flow predominatesin fixing the, form and direction of the emerging jet. With ,fliqu'id flow at high velocity, the separation of the 'f lo w "stream from the boundary which occurs at a sudden g a spray instead of a jet, and even rent jet is formed its direction will ally be as a result of microscopic roughness of minute geometrical irregularities which are practically unavoidable in the manufacture of such small orifices. These adverse effects are largely avoided in nozzles employing the orifice profiles of this invention.

The orifices of this invention have the following characteristics:

(1) Less than M inch in diameter;

(2) Gradually converge from entrance opening to emergence opening so that the ratio of inlet area to outlet area is equal to or greater than 1.414 (i.e. /2);

(3) Have an overall taper drawn from inlet to outlet :as defined later offrom 1% to 5% included angle; and (4) Conform to either a straight line (linear) taper or to a profile curvewhich ismore particularly defined .later.

Under certain circumstances also prescribed later, an elliptical entrance profile may be employed with either of the herein-described linear or curved profiles in order to reduce the effective thickness of a thick orifice plate.

Tests have shown that by employing a nozzle whose passage or passages conform to the herein-described form there is achieved a jet which is square with the dimensions of the nozzle even in the presence of normal manufacturing variations in dimension and finish, whereby parallelism in the jet streams emerging from a multipleorifice nozzle can be achieved. Furthermore the jet emerging from an orifice of this invention is stable, attains a high velocity with its vena contracta relatively remote from the orifice plate, and there is high etficiency in conversion or input energy to kinetic energy of the jet.

Figures 7 to show in enlarged cross section some orifice profiles made according to this invention and conforming to the aforementioned criteria. An arrow indicating the direction of flow is shown on each of the figures. The orifices shown in Figures 7 to 10 have a circular transverse cross section of varying diameter, the inlet radius being denoted by a, the outlet radius being denoted by b, and radius of intermediate sections being denoted by y which is a function of the distance x from the entrance' surface. The thickness of the orifice plate is denoted by L. Therefore when x=0, y=a and when x=L, -y=b in all cases. Inasmuch as the actual dimensions of the orifice will be different for every particular application and desired rate of flow, the profiles of the orifices of this invention will be defined in terms of inlet and outlet radii and the ratio x/L from which the actual shape may easily 7 be computed in any particular instance.

. The criterion that the ratio of inlet area to outlet area shall be equal to or greater than the square root of 2, i.e. greater than 1.414, means that the sides of the passage converge toward the emergence or outlet end as shown in Figures 7 to 10. By inlet area is meant the area of the orifice at the upstream surface of the orifice plate, and by outlet area is meant the area of the orifice at 'the downstream or emergence surface of the orifice plate.

tween corresponding diametrically-opposite points on the perimeter of the inletand outlet openings, as shown for example in Figure 8 by the lines 26 and 27. The pro file-of the passage intermediate the inlet and outlet may follow these lines (as in alinearly-tapered orifice) but certain curved profiles may be employed as will be described later. In Figure 7 the profile is a straight-line taper and follows. these lines, but in Figure 8 the profile .is curved and does not follow lines26 and 27 intermediate the inlet and outlet openings. Nevertheless, inorder to attain the advantages of this invention the lines 26 and 27 drawn as in Figure 8 must have a convergence of from 1 to 5% This criterion may be expressed as 1% 360(a-b)/-i-L 5% For best results it is preferred to have the overall convergence angle in the range of 2" to 2 /2 whereby the most uniformly-accurately-direct'ed jet of maximum velocity is obtained for a given input pressure and volume rate of fiow.

Referring now specifically to the orifice profile, Figure 7 shows a profile conforming to a straight line or linear taper from inlet to outlet. Figure 7 is a very much enlarged illustration and is not to scale. Such a linear taper corresponds to that given by the equation Example A By way of example an orifice having a taper given Equation 1 is given by the dimensions below:

Inlet radius a=.01 172 Outlet radius b=.00900 Thickness of orifice plate L=0.l250 Included angle=2 /2 Ratio inlet area/ outlet area=l.7

The intermediate radii are given in the followingtable:

'c z/L y Such orifices are relatively easy to make, this being done most conveniently by reaming a dlrilled hole with an appropriately-ground reamer. Whereas the jet emerging from a parallel-sided hole will be found to be erratic in direction, the jet emerging from -an orifice conforming to the above example or otherwise meeting the hereinspecified criteria is found to be accurately directed along the axis of the orifice.

As indicated above, the orifice profile may meet the previously-specified criteria with certain types of nonlinear profiles one of which is illustrated by Figure 8. The figure is of course very much enlarged and is not to scale. One such shape which has excellent characteristics as to uniformity of jet direction within manufacturing tolerances is one having a parabolic shape. The curve of this profile is that of a parabola expressed by the typical equation l l i a ds) [t In this equation y is the radius of the orifice at any transverse plane whose distance from the inlet plane is x, and L is the thickness of theorifice plate. The constants a and b for any specific nozzle are respectively the radii of the inlet and outlet openings.

Example B By way of example, an orifice having a profile given by Equation 2 is given by the dimensions below: H

Inlet radius a=.0l200 Outlet radius b=.00900 seesaw z z/L 1 SuchI'oi-ifices are easily made-by first'reaminga drilled hole "with=anappropriately-taperedreamer and subseqtiently reaming' with a reader whose profile 'is ground to the prescribed dimensions. The jet emerging fromthe above type of orifice will have even greater uniformity of directive accuracy than the linearly-tapered orifice of Another foiin of tiufved profile that rnay be employed is one conforming with the equation:

a :v a

where x and y, as well as the constants 'a, b, and Lhave the same meanings as in 'theprevioiis examples.

Eram lac Byway of xarnple,' an orifice having a profile given by Equation 3 is given by the following dimensions: Inlet radius a=.0 l;200 Outlet radius b i0 09 00 Thickness of orificeplate L=.1563 Included anglej '2j2 Ratio inlet area/ outlet area: 1.78 The intermediate radii are given in thefollowing table:

"x wi 1/ .0000v 0 01200 .0150 1 01150 0312 2 01116 .0468 .3 01081 .0024- .4 0104s .0152 .0 .01018 .0933- .0 .00091 1094 7 .00900 .1250 ".s 1 00042 .1407 .9 00020 1563 1. 0 00900 of Equations 2 and 3, as examplified by Ex- -arnpl'es' Band C, are characterized by producing a jet in wltiich;the tangential velocity of the stream line in' the jet ash-flows through the nozzle'is proportional to x to-x respectively.

Stillfurther forms of curved profiles which maybe em-' ployed are thdse corresponding to fourth-power parabolas. The following are equations of this type:

Nozzle easiest-anemi 16.1squan0ns 4,5; :a"n'd 7 will effect fluid acceleration in thenozzle-in-ihe.direction of flow which is constant-xfor Eq. ALTor-whiehiis.

, prising an elliptical entrance followed by a -IineaL-taper given bythe following dimensions: a

proportional to 0:472, Ex and Militia gEquations 55.25,

Ratio inlet area/outlet"rarea=11.78

The intermediate radii for the respective examples '1), .E, F, and 'G corresponding respectively toithejEquations '4, 5,6, and"7aregiveninthe following table:-

z I/L 1 (Ex. D) y'(Ex.-E) -1/(Ex.-'l 1 (Ex. G)

Any of thevariousnozzleprofiles'described above rnay be'provided with an elliptical entrance section. The'elliptical entrance section and the profile according to any 'of'thte above equations have a'comrnon tang nt at thqpoiut of transition. If such. elliptic entrance is employed it must satisfy two conditions in order that there be separation- "freejfiow at thewtransition'from the elliptical tothe respective noz'zle profile. orifice with an elliptical entrance profile is illustrate'din .Figure 9, and an exampleof a curved-profile orifice. with 'Anexample of a linear-taper fbeyond the elliptical entrance. and the elliptical, entrance is'not t'o be included in computing these criteria. 'It' has "been found that in order to. function properly withthe herein-disclosed orifice passages, the elliptical entrance must satisfy two conditions namely (1) the ratio of major radius 3 1 of the ellipse to minor radius 32 of the ellipse must be substantially equalto 6, and (2) the-'ratio'of minor radius 32' of the ellipse to the -radius of the I 'emergence'openingi33of the nozzle must be substantially equal to 1/2 Example H 7 Byway of example, anorifice having'a v:P fofileycorn- Elliptical entrance section:

Major radius ==I0270 "Minor'radius =.0045

? Ratio major rad/minor. rad.=-'-6 Linear-taper section:

Length L: .0780 1 Entrance radius a='.01070 Emergence radius b=.00900 Ratio-inlet 1 area/ outlet area=1i414 taper; section-i5 lPoint 401 tangencyjo'fj ellipse and," linear-tapergoeenrsgyat Theintermediate radii y given in the following table:

. 0000 01516 Elliptical entrance. .0027 01381 D0.

. 0235 01070 Point of tangency. 0365 01042 Linear taper.

In the above example x is measured from the beginning of the elliptical entrance section. It is apparent that that part of the above-dimensioned orifice preceding the point x=.0235 has less'resistance to fluid flow than it would have if the linear taper were continued to the point x=0, because the radii y are larger in the elliptical entrance section than they would be if the linear taper were continued. By employing such an elliptical entrance section it becomes possible to reduce the resistance of a thick orifice plate. The thickness of the-plate is usually dictated by strength requirements since thefnozzles of this invention operate under high pressure. For example, a multiorifice plate such as that shown inFigure 6, must have lateral dimensions consonant with those of the array of jets to be produced and therefore must be made thicker in order to hold the applied pressure over a larger area. The flow resistance of the orifices in such a plate may then be reduced by providing the orifices with a tangential elliptical entrance section as above described and C011. forming to the above-stated conditions. That part of the orifice downstream of the elliptical entrance section must conform to the criteria previously disclosed. Alternative to a linear-taper profile employed in Example H, any of the herein-described curved profiles may be combined with a tangential elliptical entrance profile fulfilling the conditions above stated.

In the foregoing examples no units are given for the dimensions inasmuch as any unit may be used provided only that the same unit is employed for all of the dimensions of any one orifice and that the unit does not result in dimensions which exceed the absolute criteria specified.

What I claim as my invention is:

1. Apparatus for producing a plurality of fine parallel liquid jets comprising an orifice plate having a plurality of perforations of circular cross section, the axes of said perforations being parallel and the maximum diameter of said perforations being less than one-sixteenth inch, and the diameter of said perforations converging gradually from entrance opening to a smaller emergence opening in such manner that the ratio of entrance-opening area to emergence-opening area is greater than 1.414, and such that the over-all convergence from the entrance opening to the emergence opening is in the range of 1 /4 to 5% 2. Apparatus for producing a plurality of fine parallel liquid jets comprising an orifice plate having a plurality of perforations of circular cross section, the axes of said perforations being parallel and the maximum diameter of said perforations being less than one-sixteenth inch, and the diameter of said perforations converging gradually from entrance opening to a smaller emergence opening in such manner that the ratio of entrance-opening area to emergence-opening area is greater than 1.414, said perforations having an over-all convergence from the entrance opening to the emergence opening in the range 134 to 10 5% and'said perforations having a profile curve con? forming substantially to that given by the equation y=a[1(x/L) ]+b(x/L) where y is the radius of the perforation at a distance x from the entrance opening, L is the distance between entrance opening and emergence opening, a is the radius of the entrance opening, and b is the radius of the emergence opening.

, 3. Apparatus for producing a plurality of fine parallel liquid jets comprising an'orifice plate having a plurality of perforations of circular cross section, the axes of said perforations being parallel and the maximum diameter of said perforations being less than one-sixteenth inch, and! the diameter of said perforations converging gradually" from entrance opening to a smaller emergence opening: in such manner that the ratio of entrance-opening area, to emergence-opening area is greater than 1.414, said perforations having an overall convergence from the entrance opening to the emergence opening in the range 1% to 5% and said perforations having a profile curve conforming substantially to that given by the equation where y is the radius of the perforation at a distance x from the entrance opening, L is the distance between entrance opening and emergence opening, a is the radius of the entrance opening, and b is the radius of the emergence opening.

4. Apparatus for producing a plurality of fine parallel liquid jets comprising an orifice plate having a plurality of perforations of circular cross section, the axes of said perforations being parallel and the maximum diameter of said perforations being less than one-sixteenth inch, and the diameter of said perforations converging gradually from entrance opening to a smaller emergence opening in such manner that the ratio of entrance-opening area to emergence-opening area is greater than 1.414, said perforations having an overall convergence from the entrance opening to the emergence opening in the range 1% to 5% and said perforations having a profile curve conforming substantially to that given by the equation perforations being parallel and the maximum diameter of said perforations being less than one-sixteenth inch, and the diameter of said perforations converging gradually from entrance opening to a smaller emergence opening in such manner that the ratio of entrance-opening area to emergence-opening area is greater than 1.414, said per-- forations having an overall convergence from the en-- trance opening to the emergence opening in the range: 1% to 5% and said perforations having a profile curve conforming substantially to that given by the equation:

where y is the radius of the perforation at a distance x" from the entrance opening, L is the distance between entrance opening and emergence opening, a is the radius of" the entrance opening, b is the radius of the emergence opening, and the exponent n has a value not less than one and not greater than three.

6. Apparatus for producing a plurality of fine parallel liquid jets comprising an orifice plate having a plurality of perforations of circular cross section, the axes of said perforations being parallel and the maximum ,diameter of said perforations being less than ,onersixteenth inch, and the diameter of said perforations converging gradually from entrance opening to a smaller emergence opening in such manner that the ratio of entrance-opening area to emergence-opening area is greater than 1.414, said perfor-ations having an overall convergence from the entrance opening to the emergence opening in the range 1% to 5% and said perforations having aprofile curve conforming substantially to that given by the equation where y is the radius .of the perforation at .adistance at from the entrance opening, L is the distance between entrance opening and emergence opening, a is .the'radius .of the, entrance opening, and b is the radius of the .emer, gence opening.

a ;7. Apparatus for producing a plurality of fine parallel liquid jets comprising an orifice plate having a plurality of perforations of circular cross section, the axes of said perforations-being parallel and the maximum diameter of said perforations being less-than one-sixteenth inch, and the diameter of said perforations converging gradually from entrance opening to a smaller emergence opening in such manner that the ratio of entrance-opening area'to emergence-opening area is greater than 1.414, said perforations having an overall convergence-from the entrance opening to the emergence opening in the range 1% to 5%3, and saidperforations having a-profile curve conforming substantially to that given by the equation where y is the radius of the perforation at a distance x from theentrance opening, L is the distance between entrance opening and emergence opening, a is the radius of the entrance opening, and b is the radius of the .emergence opening.

'8. Apparatus for producing a plurality of fine parallel liquid jets comprising an orifice plate having a plurality of .perforations of circular cross section, the axes of "said perforations being parallel and the maximum diameter of said perforations being less than one-sixteenth inch, and the diameter of said perforations converging gradually from entrance opening to a smaller emergence opening in $2 each manner ha :th a io of n r 'wp n s' a o emergence-opening area is greater than 1.414, saidv forations hav n an 9Y al conver ence from the entrance opening to the emergence opening in the range 1W to 5 4 i a sa d.perfprafipnsh vin fia pr curve conforming substantially to that given by the equation S dhi-t v t where y is the radius of the perforation at a ,distance x from the entrance opening, L is the distance between entrance opening and emergence opening, a is the radius of the entrance opening, and b is the radius of the emergence opening.

9. Apparatus for producing a plurality .of fine parallel liquid jets comprising arr orifice plate having a plurality of perforations of circular cross section, the axesof said perforations being parallel and the maximum diameter ofsaid perforations :being less than oneesixteenth inch, and the diameter of said perforations converging gradually such manner theratio of entrance-opening. are emergenceropening areais greater than 1.414, sai gl forations having an overall convergence from .the enfrom entrance opening to a smaller emergencei'opening trance openingto the emergence opening in the range" 1 to 5% ,and said perforations having a protilecurxe conforming substantially to that given lay the equation where y is the radius of the perforation at a distance it from entrance opening, L is the distance between en? trance opening and emergence opening, a is the radius of the entrance opening, and b is the radius of the emergence opening.

References Cited in the tile of this patent UNITED STATES PATENIS 

